<div class="refentry"><a id="glViewport"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glViewport — set the viewport</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glViewport</strong>(</code></td><td>GLint <var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">height</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>x</code></em>, </span><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p>
                    Specify the lower left corner of the viewport rectangle,
                    in pixels. The initial value is (0,0).
                </p></dd><dt><span class="term"><em class="parameter"><code>width</code></em>, </span><span class="term"><em class="parameter"><code>height</code></em></span></dt><dd><p>
                    Specify the width and height
                    of the viewport.
                    When a GL context is first attached to a window,
                    <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> are set to the dimensions of that
                    window.
                </p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glViewport</code> specifies the affine transformation of
            <math overflow="scroll"><mi mathvariant="italic">x</mi></math>
            and
            <math overflow="scroll"><mi mathvariant="italic">y</mi></math>
            from
            normalized device coordinates to window coordinates.
            Let
            <math overflow="scroll">

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                    <msub><mi mathvariant="italic">x</mi>
                    <mi mathvariant="italic">nd</mi>
                    </msub>
                    <msub><mi mathvariant="italic">y</mi>
                    <mi mathvariant="italic">nd</mi>
                    </msub>
                </mfenced>
            </math>
            be normalized device coordinates.
            Then the window coordinates
            <math overflow="scroll">

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                    <msub><mi mathvariant="italic">x</mi>
                    <mi mathvariant="italic">w</mi>
                    </msub>
                    <msub><mi mathvariant="italic">y</mi>
                    <mi mathvariant="italic">w</mi>
                    </msub>
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            </math>
            are computed as follows:
        </p><p>
            </p><div class="informalequation"><math overflow="scroll">

                <mrow>
                    <msub><mi mathvariant="italic">x</mi>
                    <mi mathvariant="italic">w</mi>
                    </msub>
                    <mo>=</mo>
                    <mrow>
                        <mfenced open="(" close=")">
                            <mrow>
                                <msub><mi mathvariant="italic">x</mi>
                                <mi mathvariant="italic">nd</mi>
                                </msub>
                                <mo>+</mo>
                                <mn>1</mn>
                            </mrow>
                        </mfenced>
                        <mo>⁢</mo>
                        <mfenced open="(" close=")">
                            <mfrac>
                                <mi mathvariant="italic">width</mi>
                                <mn>2</mn>
                            </mfrac>
                        </mfenced>
                        <mo>+</mo>
                        <mi mathvariant="italic">x</mi>
                    </mrow>
                </mrow>
            </math></div><p>
        </p><p>
            </p><div class="informalequation"><math overflow="scroll">

                <mrow>
                    <msub><mi mathvariant="italic">y</mi>
                    <mi mathvariant="italic">w</mi>
                    </msub>
                    <mo>=</mo>
                    <mrow>
                        <mfenced open="(" close=")">
                            <mrow>
                                <msub><mi mathvariant="italic">y</mi>
                                <mi mathvariant="italic">nd</mi>
                                </msub>
                                <mo>+</mo>
                                <mn>1</mn>
                            </mrow>
                        </mfenced>
                        <mo>⁢</mo>
                        <mfenced open="(" close=")">
                            <mfrac>
                                <mi mathvariant="italic">height</mi>
                                <mn>2</mn>
                            </mfrac>
                        </mfenced>
                        <mo>+</mo>
                        <mi mathvariant="italic">y</mi>
                    </mrow>
                </mrow>
            </math></div><p>
        </p><p>
            Viewport width and height are silently clamped
            to a range that depends on the implementation.
            To query this range, call <a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument
            <code class="constant">GL_MAX_VIEWPORT_DIMS</code>.
        </p></div><div class="refsect1"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if either <em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em> is negative.
        </p></div><div class="refsect1"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_VIEWPORT</code>
        </p><p>
            <a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAX_VIEWPORT_DIMS</code>
        </p></div>
        {$pipelinestall}{$examples}
        <div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glDepthRangef"><span class="citerefentry"><span class="refentrytitle">glDepthRangef</span></span></a>
        </p></div><div class="refsect1"><div id="Copyright"><h2>Copyright</h2><p>
            Copyright © 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/" target="_top">https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></div>
